The present invention relates to a chip type piezoelectric resonator and a manufacturing method thereof.
In a conventional chip type piezoelectric resonator, a resonator element is inserted in a concave portion of a box-type case, and bonded to the case by conductive adhesive. The concave portion of the case is provided with internal electrodes on inner surfaces of the ends of the concave portion. The internal electrodes are connected with electrodes of the resonator element. The concave portion has a deeper concave portion in its central part for defining a vibration space between the case and the resonator element. A cover is bonded to an upper surface of the case to seal the interior of the case. Thereafter external electrodes are provided on outer surfaces of the case and the cover, to be connected to the internal electrodes.
The aforementioned piezoelectric resonator is manufactured by the following method: first, a number of concave portions are formed in an upper surface of a mother plate, and internal electrodes are formed on both ends of each of the concave portions. Next, resonator elements are inserted one by one in the respective concave portions, so that both end portions of the resonator elements can be bonded to the ends of the concave portions by conductive adhesive. Thus, electrodes of the resonator elements are connected with the internal electrodes. Then, a mother plate cover is bonded to an upper surface of the mother plate to seal the concave portions. Thereafter, the mother plates are integrally cut into independent chips. Each independent chip is then provided with an input external electrode and an output external electrode to be connected with the internal electrode on the outer surface of the chip.
If necessary, a ground electrode may also be formed in addition to the input and the output electrodes.
However, the aforementioned manufacturing method is inferior because the resonator elements are inserted one by one in the concave portions of the mother plate and the conductive adhesive is supplied to the respective concave portions one by one. In particular, it is extremely difficult to correctly insert such small-sized resonator elements, which are several millimeters in length for example, in the very small concave portions. Further, because the adhesive must be applied to both ends of each concave portion alone, it is necessary to apply the conductive adhesive twice to every concave portion. In addition, clearances must be defined between the inner surfaces of the concave portions and the resonator elements in order to smoothly insert the elements, which prevents further miniaturization.